In the 16th century, an Italian engineer modified two ships into devastating weapons known as hellburners, or “infernal furnaces,” with unprecedented destructive power.
During the age of wooden sailing ships, fire was the number one enemy of sailors. In wartime, fire was also extensively used to sink enemy vessels.
Illustration of a bridge over the Scheldt River built as a barricade during the siege of Antwerp. (Image: Amusing Planet).
A formidable strategy initiated by the ancient Greeks involved setting fire to a ship loaded with flammable materials such as tar and pitch, then sending it towards the enemy. These fire ships could create horrifying chaos for the opponent at alarming speeds. By the 7th century, the Greeks discovered that mixing naphtha with quicklime would produce a burning mixture that ignited spontaneously upon contact with water. This was the world’s first incendiary weapon.
Advancements in shipbuilding and the invention of gunpowder enhanced the power of this type of weapon. Fire ships were no longer just tools for burning enemy fleets or ports; they became floating bombs designed to destroy as many vessels as possible with powerful explosions.
In the winter of 1585, the city of Antwerp was besieged by the army of Alexander Farnese. Farnese, commander of the Habsburg forces in the Spanish-controlled Netherlands, constructed a bridge over the Scheldt River, cutting off the city’s water route. The aim was to starve the city’s inhabitants. To overcome this obstacle, the Dutch hired Federigo Giambelli, an Italian military engineer renowned for his knowledge across multiple scientific fields.
Giambelli promised to destroy the bridge and requested three large merchant ships from the city’s fleet. His request was denied, and he was only provided two smaller vessels, Fortuyn and Hoop. Nevertheless, he was determined to demonstrate his capabilities even with limited resources.
Giambelli transformed the two ships into the largest bombs in Europe at that time, referring to them as hellburners. Inside the ship’s hold, Giambelli constructed a “combustion chamber” measuring 12 meters long and 5 meters wide, built with bricks and mortar, with walls 1.5 meters thick. He packed the chamber with 3 tons of high-quality gunpowder and sealed it with a roof made from old leaded gravestones. Above this chamber and in the surrounding space, he filled the ship with stones, iron fragments, and other materials to act as shrapnel. The entire setup was covered with traditional wooden decking to give the appearance of an ordinary ship.
The Fortuyn was equipped with a slow fuse—a length of stable burning cord that would detonate the bomb after a predetermined time. Meanwhile, the fuse on the Hoop was a “technical marvel.” Giambelli enlisted a clockmaker in Antwerp to create a mechanical timer combined with a flint ignition mechanism to detonate the gunpowder at the exact appointed time. This was the first timed bomb in history.
Illustration of the hellburner exploding in Antwerp in 1585. (Image: Amusing Planet)
Giambelli planned to release about 30 fire ships downriver in successive waves to draw the attention of the Spanish forces until the Fortuyn and Hoop could crash into the bridge. However, on the night of April 4, 1585, the officer in charge of the operation mistakenly released all the fire ships at once, followed by the two hellburners.
The Fortuyn ran aground on the riverbank before reaching the bridge. Its bomb detonated weakly, causing minimal damage to the Spanish forces.
Meanwhile, the Hoop charged straight toward the bridge and crashed violently. As the timer expired, a horrific explosion instantly destroyed the ship and took the lives of 800 Spanish soldiers. A large section of the bridge also vanished. Subsequently, millions of shattered gravestones and iron fragments that Giambelli had packed into the ship’s hold rained down from the sky. Houses kilometers away collapsed, and the blast was heard 35 kilometers away.
Despite the attack’s terrifying power, the Dutch were unable to capitalize on the opportunity and allowed the Spanish to rebuild their wooden barricade. Antwerp surrendered just four months later.
Military historian Robert L. O’Connell referred to the hellburner as the first weapon of mass destruction in history. It was also the largest man-made explosion set off at that time.
